1. Field of the Invention
The present invention relates generally to the construction of a chair suitable for use in an office environment, and more particularly to a chair which is designed to have adjustable movement of the seat and back as the user changes position in the chair, and which is constructed in a highly novel and economic manner.
2. Description of the Related Art
Seating articles, such as chairs, often include mechanisms to provide position adjustment of various parts of the chairs. This is particularly true of chairs used in office environments where office workers are frequently seated over long periods of time. These adjustments can include, for example, modification of the chair seat relative to floor level, modification of chair back rest angle relative to an initial vertical position, and modification of chair seat angle relative to an initial horizontal position. All of these adjustments can contribute to the comfort of the chair user by selectively altering the user's body position when seated. Typically, these adjustments are accomplished by chair control mechanisms which include linkage systems of various types including spring biasing means.
A form of chair control system that has proved to be comfortable for the user is disclosed in early U.S. Pat. No. 2,083,838. This patent illustrates a body weight actuated chair wherein the rear of the seat raises slightly as the chair back tilts rearwardly. This allows the user to recline somewhat in the chair while his or her feet remain placed on the floor. The w eight of the user's body against the chair back acts through a slide mechanism to raise the seat back. While this construction allows for a degree of comfort to the user a disadvantage of the chair is that the slide mechanism is subject to wear and consequent binding over periods of use. Therefore, in practice it has a somewhat limited life and is lacking in reliability.
In more recent times a chair has been disclosed in U.S. Pat. No. 5,486,035 issued Jan. 23, 1996 to Koepke et al. wherein the chair has a reclinable back, and the seat and back are interconnected by a stiff resiliently flexible transition connection connecting the seat rear portion and the back lower portion. The seat front portion is pivotably mounted on a support whereby reclining of the back raises the seat rear portion producing an occupant weight operated reclinable chair having a substantially uniform back reclining force requirement throughout the reclining range of motion.
The Koepke et al. chair as just described offers considerable advantages over the chair disclosed in U.S. Pat. No. 2,083,838 essentially because it has very few moving parts which can be subject to wear. Basically, the chair is constructed with a support arm beneath the seat that has a seat front pivot and a rear pivot. These pivots are the only moving parts. Accordingly, the Koepke et al. chair can be readily constructed by known manufacturing methods and is highly reliable in use, although details of the chair construction are not specifically disclosed in the '035 patent.
In conventional office chair construction it is sometimes economical to manufacture the seat and back of the chair using molded plastic shells. In one such form of construction, the seat and back may each include two mating contoured shells, namely an upholstery shell and an outer shell. The upholstery shell in this construction is typically provided with suitable padding covered over by a layer of fabric or other similar upholstery material. The fabric layer, or the like, typically wraps over the peripheral edges of the shell and is fastened on the rear side of the shell. The outer shell which may or may not be similarly upholstered is then fastened to the back side of the upholstery shell thereby concealing the fastened edges of the fabric, lending an aesthetically pleasing finished appearance. A number of methods exist for fastening the shells together to create a finished chair. Such methods include the use of screws and snap fitting means cooperating between the two shells. However, the use of screws, for example, particularly if the screws are exposed to view is not as desirable aesthetically as a screwless appearance. Moreover, snap fitting means can make it difficult to take the chair apart once it is assembled, such as for reupholstering. Accordingly, it is desirable to construct a chair, particularly of the aforementioned type having a seat front pivot wherein the upholstery shell and outer shell are fitted together with a minimum of screw type fasteners. It is further desirable to provide such a chair wherein the upholstery shell and outer shell can be readily assembled and disassembled with a minimum of manual effort. Still further, it is desirable to provide such a chair wherein the connection means of the upholstery shell and outer shell can be readily manufactured in a cost-effective manner and is highly reliable in use.